Although long promoted as a valuable management tool, few researchers use local ecological knowledge (LEK) to manage plant invasions, and methodological challenges associated with this use have been little explored. Here I summarize results of two studies using LEK from salt hay farmers to manage Phragmites australis invasion in tidal marshes. The first study used LEK to develop strategies to prevent invasion. Local accounts were used to construct causal histories of the invasion, which in turn were validated through a series of greenhouse and field experiments. The second study adapted indigenously developed control methods to restoration settings. Salt hay farmers were asked whether they knew of successful eradication methods. Their methods were evaluated in marshes with large clones as well as recently restored marshes experiencing reinvasion.
The farmers’ accounts stated that rhizome dispersal and burial along ditches led to establishment. However, the accounts could not elucidate why this establishment pattern existed, and were too site specific to develop preventative strategies. Subsequent field and greenhouse experiments found that shoots would not emerge without rhizome burial in well-drained areas, and shoot mortality approached 100% when exposed to salinity about 18‰. This mechanistic understanding proved robust for understanding how activities could lead to establishment at a variety of sites, and thus could be used in preventative strategies. The farmers’ accounts suggested Phragmites clones could be eradicated through repeated cutting. However, this knowledge was held by only one individual, and the technique was never rigorously evaluated by any of the farmers. Field evaluations at two restoration sites suggested that repeated cutting eradicated reinvading clones, and therefore could be used as a low-cost control method in restoration settings. These studies suggest LEK has several features that could hinder its use in invasive-species management. These include: 1) small populations of resource users with useful knowledge, 2) uneven distribution of LEK among resource users, 3) limited ability to translate knowledge into practice, 4) limited ability of resource users to make key observations, and 5) site-specific nature of accounts. Nevertheless, LEK could be useful for invasive species management if its validity can be rigorously evaluated and if results can be extrapolated to management settings.